a) Field of the Invention
The present invention relates to a fault detection system and method, and more particularly to a fault detection system for a movable elongate member, such as a conveyor belt by which rips or other faults in the belt can be detected.
b) Background Art
Large industrial conveyor belts have a variety of applications such as in commercial mining operations or other situations where large quantities of ore or other material are to be moved from one location to another. Such belts are commonly made of rubber or synthetic rubber, and steel reinforcing cables are generally embedded in the belt and extend along the length thereof. It sometimes happens that rips extending along the lengthwise axis of the belt will develop, or other damage to the belt will occur. It is highly desirable that such rips or damage be identified at an early time, so that timely remedial steps can be taken.
One method which has been employed to detect such rips or other damages is to embed in the belt a rectangular loop of wire or other conductor so as to extend across width of the belt and enclose a significant area of the belt, and adding a sensing apparatus of some kind which detects when the wire is broken.
It is the object of the present invention to provide a fault-monitoring and sensing system, particularly adapted for use in such large industrial conveyor belts, with this system having a desirable balance of operating features. More particularly, in the system of the present invention, three situations are able to be detected at spaced detecting locations along the length of the belt. (In the following text the fault to be detected will sometimes be designated as a xe2x80x9cripxe2x80x9d along a lengthwise axis, with the understanding that this is meant to include other types of damage.) The three situations to be detected are:
i. a satisfactory condition where the fault detector at a detecting location in the belt, transmits an xe2x80x9cokayxe2x80x9d signal which indicates that the fault detector is functioning and no rip has been detected;
ii. a fault-indicating condition where a rip has occurred in the belt, and the sensor is operating to indicate this rip or other damage;
iii. a condition where no indicating signal is transmitted when one would be expected, which would indicate that the sensing apparatus at that location is damaged and is not capable of indicating either no damage or a damaged condition.
Thus, one of the major benefits of this system is that it has been made so as to be xe2x80x9cself-diagnosticxe2x80x9d, in that it has a means for providing continuous feedback on the condition of the fault detectors themselves, in addition to ascertaining the fault or no-fault condition of the belt as indicated by the sensor.
The conveyor belt has a longitudinal axis, a transverse axis, and first and second side portions.
The monitoring system comprises first a fault-sensing system, comprising a plurality of fault-sensing units. These are located at spaced fault-sensing locations along the longitudinal axis of the belt.
Each of the fault-sensing units comprises an electrically conductive fault-responsive component which extends between the side portions of the belt and which has an intact condition in a belt no-fault condition, and a non-intact condition in a belt fault condition. There is also a fault-sensing component that comprises a fault-sensing circuit. The fault-sensing circuit is operatively connected to the fault-responsive component, and arranged to provide no-fault or fault responses corresponding to the intact and non-intact conditions, respectively.
The fault-monitoring section is arranged to transmit interrogating signals to the fault-sensing units and to receive the fault or no-fault responses from the sensing units. The fault-monitoring section in turn generates a reporting signal corresponding to the responses from the sensing unit.
Thus, as the belt travels and the fault-sensing units pass by the fault-monitoring section, the fault or no-fault condition of the belt at the location of the fault-sensing units is detected.
In a preferred embodiment, the fault-responsive component provides an electrically conductive path extending between the first and second side portions of the belt and connecting to the fault-sensing circuit. The fault-sensing circuit has a first operating mode which functions with the conductive path of the fault-responsive component intact to provide no-fault responses, and having a second operating mode which functions with the conductive path in the fault-responsive component in a non-intact condition to provide a fault response.
The electrically conductive fault-responsive component comprises a conductive loop having two end connecting portions which connect to the fault-sensing circuit. Thus, there is formed a bypass connection, and with the fault-responsive component in its non-intact condition, the electrically conductive path is interrupted and the bypass connection becomes nonfunctional.
In a preferred form, the bypass connection is in parallel with at least one circuit component of the fault-sensing circuit. In the specific embodiment, the fault-sensing circuit comprises, at least in part, a resonant circuit portion which operates at a first resonant frequency with the fault-responsive component in the intact condition, and operates at a second resonant frequency with the fault-responsive component in the second non-intact condition. The fault-monitoring section comprises a receiving/transmitting portion which is responsive to the first and second frequencies in order to generate a reporting signal corresponding to the frequency of the response received from the fault-receiving component.
In a specific configuration, the fault-sensing circuit comprises a coil portion and a capacitance portion. The electrically conductive fault-responsive component has an operative connection with at least said capacitance portion in a manner that in the no-fault condition, the capacitance portion has a first capacitance value, and in the fault condition, the capacitance portion has a second capacitance value, in order to provide the first and second frequency outputs.
In one arrangement, the electrically conductive fault-responsive component is in series with at least one capacitor of the capacitance portion. In another arrangement, the electrically conductive fault-responsive component is in parallel with at least one capacitor of the capacitance portion.
In the preferred form, the fault-sensing units are passive, and the monitoring section comprises a detecting section arranged to transmit an interrogating signal which energizes the fault-sensing unit. The interrogating signal is arranged to energize the fault-sensing circuit in each of the no-fault operating modes of the fault-sensing circuit and in the fault operating mode of the fault-sensing circuit to cause the no-fault or fault response.
The interrogating signal comprises first and second signal components matching characteristics of the fault-sensing circuit in a no-fault or fault-responding operating mode to generate the no-fault or fault condition. More specifically, the detecting section is arranged to transmit the interrogating signal having first and second frequency components to energize the fault-detecting circuit operating in first or second frequency modes to transmit a no-fault response or a fault response corresponding to the first and second frequencies, respectively.
In a preferred form, the fault-monitoring section is arranged to transmit the interrogating signal or signals as a wave form having at least first and second frequency components, and said fault-sensing circuit has a resonant frequency portion which operates at a first resonant frequency with the fault-responsive component in the intact condition, and operates at a second resonant frequency with the fault-responsive component in the non-intact condition.
The system is characterized so that when on of the fault-sensing units is in proximity to the fault-monitoring section, and when the fault-sensing circuit is operating at the first resonant frequency with the fault-responsive component in the intact condition, the resonant circuit portion draws energy from the first frequency component of the fault-monitoring sections to provide the response. When the fault-sensing circuitry is operating at the second resonant frequency, with the fault-responsive component in the non-intact condition, energy is drawn from the second frequency component of the fault-monitoring section to provide the response.
The fault-monitoring section is arranged to generate a reporting signal of the no-fault or fault-condition in response to the change in the energy level of either the first or second frequency components of the fault-monitoring section.
In the preferred form of the present invention, the fault-monitoring section comprises a detecting section having first and second detecting subsections, with one of said subsections generating an interrogating wave form of the first frequency, and the second subsection generating an interrogating wave form of the second frequency. Each of these subsections comprises a signal generator which produces signal pulses that are directed to a drive coil. The drive coil in turn is coupled to an idler section that comprises an idler coil and a capacitor. A pickup coil is in turn coupled to the idler coil 64 and in turn is operatively connected to a signal processing section.
In the method of the present invention, there is first positioned a plurality of the fault-sensing units at spaced fault-sensing locations along the longitudinal axis of the belt. The belt is moved along a belt-traveling path aligned with the longitudinal axis, with the fault-sensing components being positioned to move along a monitoring path.
The fault-monitoring section is positioned at a monitoring location adjacent to the monitoring path. The fault-monitoring section transmits the interrogating signals to the fault-sensing units as the units are passing by the monitoring location to initiate and receive the fault or no-fault responses from the sensing unit. These are in turn directed to a processing unit to generate a reporting signal corresponding to response or responses from the sensing unit.
Other features of the present invention will be apparent from the following detailed description.